Window grilles are mounted on inside surfaces of window panes to have the effect of dividing the panes into groups of smaller panes or "lights". The grilles give an appearance of a traditional pattern of small panes, a look that continues to be popular in new homes.
Generally, the grilles are manufactured and shipped to builders in the form of precut sticks with half-lap joints for assembling the sticks together in a desired pattern. The builders assemble and sometimes finish the grilles before installing them in windows. Although most of the finishing work on the grilles is done by either builders or home owners, some grille sticks are shipped to builders in a prefinished condition.
However, prefinishing of the grille sticks can add considerable cost to their manufacture because extra care must be taken to prevent paints or other finishes from entering the half-lapped joints. Masking of the joints to protect them from the finishes can be very time consuming and difficult to accomplish with consistent results. Also, any finishes applied to the grille sticks are generally applied to all sides of the sticks because it would be prohibitively expensive to mask whole sides of the sticks.
Nevertheless, home owners often prefer different finishes on the opposite sides of window grilles. For example, paint is often preferred on the side of the grille visible from the exterior of the home, whereas a stain or clear varnish is preferred on the interior side of the same grille, or two different colors of paint are preferred on the opposite sides of the grille.
Since it has not been practical for the manufacturers of grille sticks to provide the two different finishes on opposite sides of window grilles, the task of applying the desired finishes has been left to builders or home owners, neither of which are particularly well equipped to do a good job without expending a considerable amount of time. Of course, professional painters can do the job, but this adds considerable incremental cost to the grilles, which are otherwise a rather inexpensive window treatment.